This invention relates to a throttle opener for carburetors, and more particularly to an improved device for controlling the movement of a throttle valve of an engine on decel.
When the throttle valve of a vehicle powered by an internal combustion engine is suddenly closed, a high vacuum is exerted in the induction system. This high vacuum acts upon the fuel discharge circuits and tends to draw an overly rich mixture into the intake system under such running conditions. To avoid these difficulties, it has been proposed to provide a throttle positioning device which will either prevent or retard the complete closure of the throttle valve under such conditions. Such devices normally hold the throttle valve from reaching its fully closed or idle position for a period of time after the throttle valve has been suddenly closed. The prior art type of throttle positioning devices have normally employed a vacuum motor that is responsive to the intake vacuum downstream of the throttle valve. Thus, when the throttle valve is suddenly closed, a high vacuum will be exerted in the intake system and the vacuum motor is actuated so as to prevent full closure of the throttle valve. Such arrangements have, however, certain disadvantages. For example, if the throttle valve closure is delayed for too long a period of time, there will be substantially no engine braking. Also, such delayed closure will cause the engine to race under certain conditions. For example, if the throttle is rapidly opened and closed when the vehicle is not being driven, the action of the throttle positioner will cause over-revving of the engine.
In order to preclude these problems, it has been proposed to employ a device that is responsive to either vehicle speed, transmission condition or a combination of these factors which will override the operation of the throttle positioner. Such devices further complicate the overall system, add to its cost, and increase the likelihood of malfunction.
It is, therefore, a principal object of this invention to provide a throttle valve positioner which is more sensitive to actual engine conditions.
It is another object of this invention to provide a throttle valve positioner which retards the rate of closure of the throttle valve under sudden decelerations but which does not unduly delay the closing of the throttle valve and also which will not hold the throttle valve open under conditions in which such action is unnecessary.